The goal of this project is to develop a clinical microwave phased array applicator system for hyperthermia therapy in deep-seated tumors. The proposed work seeks to continue development of a novel phase-controlled system for hyperthermia induction. The therapeutic effectiveness of ionizing radiation therapy can be improved by the focused application of heat to the tumor region. The use of microwaves for the generation of local and regional hyperthermia has been successfully applied in clinical studies. However, current designs for microwave applicators heat only superficial tumors and must be mechanically moved in order to change power distribution in the tumor and surrounding normal tissues. The specific aims of the proposed Phase II program are designed to complete development of new techniques for producing tumor hyperthermia using microwaves. Phase I efforts have resulted in new designs for microwave phased array hyperthermia applicators and development of working laboratory prototype applicators utilizing microstrip patches and waveguides. In Phase II, a clinical prototype system will be developed consisiting of phased array applicators, solid-state power amplifiers, computer control system, thermometry mapping, and human-engineered interactive operation. This new phased array system will have the capability of focusing energy more effectively in tissue than presently available clinical devices and the location of the focus will be electronically rather than mechanically scanned to produce a uniform tumor temperature distribution without overheating surrounding normal tissues. The developed system will be tested in phantoms and experimental animal models.